1. Field of the Invention
This invention relates to a method communicating between a first and a second node in a communications network, each of the nodes comprising a SIP client. The invention also relates to a communications network node comprising a SIP client arranged to implementing the method, a computer program for controlling the communications network node and a communications network incorporating such a node. The invention also relates to a method of setting up a conference call between more than two parties using the method of communication.
2. Description of the Prior Art
Session initiation protocol (SIP) is used to set up communications sessions such as data or voice communication sessions between two SIP clients. SIP is a simple signalling protocol for Internet conferencing and telephony and details about SIP are available on the Internet at www.cs.columbia.edu\˜hgs\sip\ and also in the document “Request for comments (RFC) 2543 SIP: Session Initiation Protocol” Handley, et al. March 1999 available from the internet site listed above. As well as being used to set up communications sessions, SIP is also used to modify and terminate sessions with one or more participants. For example, these sessions may be Internet multimedia conferences, internet telephone calls and multimedia distribution. Communication between members of a session is via multicast or a mesh of unicast relations, or a combination of these. Using SIP, session descriptions that allow participants to agree on a set of compatible media types may be used. Also, user mobility is supported by proxying and redirecting requests to a user's current location. As well as this SIP is not tied to any particular conference control protocol. However, the standard SIP protocol only supports a limited set of functionality and this is a significant drawback.
Multimedia teleconferencing and other conference calls are a complicated service for an end user to use. Because of this complexity many conferences experience problems or interrupts as various users set up the calls incorrectly. Central manual operators are often required to set-up the calls and this is expensive.
It is accordingly an object of the present invention to provide a method of communicating between a first and a second node in a communications network where those nodes each comprise a SIP client, which overcomes or at least mitigates one or more of the problems noted above.